I have upgraded the following but need some help from you car audio peeople

I have the base streo which I have coded to hifi.
I have changed the front mids to Logic 7 mids and added Logic 7 tweeters
Rear speakers are still OEM

I have used a Techincs harness on the back of my HU, ran all the relavant wires down the passenger side and into the boot.

I am using a JL audio XD400.4 amp which has been mounted where the CD changer goes.

I have used 4AWG wiring - the earth cable comes off the amo and onto the chassis (wire is 15cm long)

The power cable is connected onto the main battery terminal, runs alongside the arch and acorss where my DAB/bluetooth is and then along the left arch and into the amp.

The wiring loom from the harness runs down the passenger side, up the rear passenger side pillar/cusion over the arch and into the amp (I have tried to keep the maximum distance between that and the power cable and where it does cross have kept wires at right angles)

The 4 channel amp
Channel 1 & 2 = front right and left speaker
Channel 3 & 4 = front left and right under seat subs

I have only one pair of RCA going into the amp (running it in 2 channel mode) - Red RCA = Front right speaker / Black RCA Front left speaker

From the HU harness I have connected the left rear speaker back up to the loom going back to the HU and likewise for the left right rear speaker using block connectors.

Now when I switch the ignition on I get a loudi'ish hissing/buzzing noise coming from the passenger front speaker/ The right side is fine no hissing/buzzing noise. The buzzing noise is still there when switching engine on.

I do get a bit of alternator whine coming through as I rev the car but cannot hear it while the volume is loud.

the buzzing noie gets worse as I turn the gain up so at the moment the gain for the front speakers is on 1/4 and subs just over 1/4

The buzzing noise has stumped me as I plan to re check all my wiring tommorow/RCA connections. I plan to connect a spare speaker and connect it to each channel to see if I can eliminate the noise

But anyone suggest what this buzzing noise could be and what i can do to take a look?

Thanks Sam, I will try the above tommorow and report back. I was running out of light today to troubleshoot some ideas

I left the amp settings to my cousin as he is more knowledgable than me but he did say he had turned the gain down for the front speakers for the meantime as the buzzing from the passenger side was loud when the gain was turned more than 1/4. Once I sort this issue out then he wil correctly set up up the gain settings for me

As I need my car for work I am happy to leave it 1/4 until I can sort out this buzzing noise

Thanks Sam, I will try the above tommorow and report back. I was running out of light today to troubleshoot some ideas

I left the amp settings to my cousin as he is more knowledgable than me but he did say he had turned the gain down for the front speakers for the meantime as the buzzing from the passenger side was loud when the gain was turned more than 1/4. Once I sort this issue out then he wil correctly set up up the gain settings for me

As I need my car for work I am happy to leave it 1/4 until I can sort out this buzzing noise

When you say check left tweeter why do you say that?

Gains are setup on max volume with treble and bass at 0, sub vol at 3.
I think your gain is high as well.

Re: tweeter, if nothing helps disconnect the tweeter from L7 mid to see if that is causing the issue.

How much should I set gain for the speaker and the subs? less than 1/4?

As I have idrive I cannot tell what volume I am on at the HU as it does not show a numerical value

Your cousin should be able to do it with multi-meter.
Or if you are good enough to identify soft / hard clipping, then you can do it without multi-meter.

You have rear speakers though to start and identify the max volume of HU.
Turn down the gains to minimum.
Turn the amp to 4 channel mode.
RCA to Ch 1&2.
Turn on the HU and volume to max (use rear speakers to hear when sound is not increading any further.)

Set your gains for mids.

Once you are done with above, turn off the HU / car and swith RCA cables to Ch3&4.
Repeat the same procedure as above to set gains for your sub.

Once you are finished with all put the cables to Ch1&2 and switch the input mode to Ch1&2 so that all can take the input from it.

Many thanks for writing a detailed reply, he did have his multimeter out and was using it but our main concern was the buzzing noise.

I have changed over the RCA phono plugs to plastic ones which I bought from Maplin - I carefully soldered them on to ensure polarities did not touch - back in the car and nope it did not make a difference buzzing noise still there.

Then I swapped the RCA plugs around, into the right channel I plugged the left RCA and vice versa - the buzzing noise went from the passenger side to the drivers side and the passenger side had no buzz

Changed the amp settings/gains to reflect the change and the buzzing still came from the passenger side.

This leads me to think something is wrong from the harness/HU end but as I got back late and did the above in the dark (5pm) with a flashlight I will have to pull out the HU again tommorow and check connections behind.

Also I have noticed when I have the volume on low I do suffer form alternator whine coming through speakers is this the norm?

Then I swapped the RCA plugs around, into the right channel I plugged the left RCA and vice versa - the buzzing noise went from the passenger side to the drivers side and the passenger side had no buzz

Most likely you have the answer.
Try to take phono RCA out of your iphone and plug it directly to your amp.
If there is no buzzing sound in your left mid, then certainly problem is somewhere b.w HU and source of input to amp on left side wiring.

Quote:

Originally Posted by mistryn

Also I have noticed when I have the volume on low I do suffer form alternator whine coming through speakers is this the norm?

I think your harness is picking up noise on its way to amp. Check it again especially on passenger side footwell.

You are correct in assuming the passenger side is the noisy side of the
car. Yes you run the power wires directly to the battery for all your aftermarket stuff with a fuse. There is some debate at to how noisy the
chassis grounds are. One of the professional installers on this board suggests
running both the power and ground directly to the battery and since I bought his kit that's what I did and I don't have any noise. People that have used the other grounds have had mixed results. I think you only need to follow the existing wire routes to get good results but I guess is you started out with a base system they might not be there. I think most are buying the Technic Harness and he has a route plan with that. If you look in the Audio Contents
thread there should be some examples

I have attached the ground to one of the bolt holes where the CD changer would sit so may look at another ground point - I did sand it down to bare metal but that might not be a good point.

Also I have ran both looms down the passenger side

Quote:

The standard layout install of the Stereo harness that I use is attached below...

I normally run the output extension cable under the center console left side, under the driver seat and then door sills towards the trunk via the rear seat. The input extension cable is run the same way but on the right side. At the same time time I run the center and underseat woofers wires.

I am going to pull the HU out tommorow check the connections and if the noise still persits then re route the wiring loom as per in the thread down the centre console by routing the outgoing down one side and the amped cable down the other side of the console

I dont have a phone jack to rca adapter but may pick one up from maplins and try it with my iphone in to the rca jack.

3- You can follow Technics guide to route harness if you are able to pass the wires through the centre.

Personally it is a lot easier if you pass it from the passenger side. I have run it on my passenger side and zero noise issues.
But mind you, in my second version of harness I have replaced the wires to RCA cable. It protects the signals as RCA cable is shielded and hence zero noise issues.

And please bear in mind that USA passenger side is Uk driver side where all the power cable runs. So on that point, you are safe.

I reckon your passenger side cable is picking up the intereference from something.

In that picture is the earth wire coming from the amp > earth point on drivers side > to negative on battery terminal?

No. In my pic, there are two earth cables running to two amps.
You only need to connect earth cable to that earth point and not to the battery.
I have experimented attaching the earth cable to battery directly and no much difference IMO.

This morning I plugged in my iphone via a phone > RCA plug adapter - Buzzing noise was gone. This led me to think problems with wiring fro back of HU to the amp - it picking up interference on the way

So I pulled out my HU, re routed the wiring loom under the passenger footwell rather than under the glove box - buzzing noise 85% gone. Then I re routed my earth wire as to makkans post above and did a bit of tidying up with wires. As a result 90% buzzing noise gone. I had a spare ground loop isolater (yes I know some of you will be shaking your heads at me) I decided to plug that in and buzzing noise 95% gone. You can still hear a very faint buzzing noise when on mute but not when volume on whereas before the buzzing noise was constant no matter what volume.

Thanks to everyone really appreciate your help

I will be typing up a mini how to if anyone is interested as I took some pictures along the way

oh well haha I was in that frame of mind where I did not want to cut bits out of the car and was going along the lines I will make it fit but ended up cutting and if I had done that earlier would have saved me a lot of time

So I pulled out my HU, re routed the wiring loom under the passenger footwell rather than under the glove box - buzzing noise 85% gone. Then I re routed my earth wire as to makkans post above and did a bit of tidying up with wires. As a result 90% buzzing noise gone. I had a spare ground loop isolater (yes I know some of you will be shaking your heads at me) I decided to plug that in and buzzing noise 95% gone.

Glad that you sorted it. For all others who are planning to run harness, please run it:
-HU to passenger side
-On passenger side, it should pass deep under the passenger footwell carpet. If you keep it superficial or relatively up, there is a fuse box, junction box and chances are that it will pick interference.
- Connect your earth to earth terminals or directly to battery as per your preferences.

Hope that make sense.

Quote:

Originally Posted by mistryn

You can still hear a very faint buzzing noise when on mute but not when volume on whereas before the buzzing noise was constant no matter what volume.

That is normal. Only DSP, or possibly clean sweep will take it out.
It happens on max volume most of the time.

I didn't think I would be saving much money (just a bit on a less complex harness, but still need amp+DSP+speakers), it just meant not removing and refitting the HU. Whichever harness is used, it would still be routed the same way (just less of it in the simpler one). Why would you get more noise?

I didn't think I would be saving much money (just a bit on a less complex harness, but still need amp+DSP+speakers), it just meant not removing and refitting the HU. Whichever harness is used, it would still be routed the same way (just less of it in the simpler one). Why would you get more noise?

If you are having DSP in your sound system (and also in that thread which you posted), it should help to reduce the noise.

I have routed the wires to each side of car (L to passenger side & R to driver side) and had the noise.
I reckon it was due to the fact that all the major wires passes on driver side of the car and R side was picking up the noise.

The noise in my car was associated to intereference from FRM (light) module / its wirings. As each time I read and code that module on my car, that noise increased.